[Why]
sg_alloc_table_from_pages alloc too large continuous PFN pages under xen dom0.
However, xen should check continuous MFN pages in range_straddles_page_boundary.
When range_straddles_page_boundary return false, some cases fall back into
swiotlb process and the continuous allocable page is not enough.
[How]
In fact, xen swiotlb set max_segment default value as UINT_MAX and
xen_swiotlb_init_early already change the value to PAGE_SIZE under xen dom0.
However amdgpu driver doesn't use the value, which may cause issue such
as swiotlb buffer full. Add amd_sg_segment_size according to iommu setting,
the details are as follows:
iommu setting | amd_sg_segment_size
-------------------------------------------------------------------------------
iommu=on | UINT_MAX
iommu=off && swiotlb on | IO_TLB_DEFAULT_SIZE(64M)
xen_swiotlb on | PAGE_SIZE(4K)
-------------------------------------------------------------------------------
Signed-off-by: Shane Xiao <shane.xiao@xxxxxxx>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 22 ++++++++++++++++++++--
1 file changed, 20 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index 134575a3893c..d081fcd22d6b 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -80,6 +80,23 @@ static int amdgpu_ttm_init_on_chip(struct amdgpu_device *adev,
false, size_in_page);
}
+static inline unsigned int amdgpu_sg_segment_size(void)
+{
+ unsigned int size = swiotlb_max_segment();
+
+ /* size=0 when amd iommu enabled */
+ if (size == 0)
+ size = UINT_MAX;
+
+ size = rounddown(size, PAGE_SIZE);
+ /* swiotlb_max_segment_size can return 1 byte when it means one page. */
+ if (size < PAGE_SIZE)
+ size = PAGE_SIZE;
+
+ return size;
+}
+
+
/**
* amdgpu_evict_flags - Compute placement flags
*
@@ -760,9 +777,10 @@ static int amdgpu_ttm_tt_pin_userptr(struct ttm_device *bdev,
int r;
/* Allocate an SG array and squash pages into it */
- r = sg_alloc_table_from_pages(ttm->sg, ttm->pages, ttm->num_pages, 0,
- (u64)ttm->num_pages << PAGE_SHIFT,
+ r = sg_alloc_table_from_pages_segment(ttm->sg, ttm->pages, ttm->num_pages, 0,
+ (u64)ttm->num_pages << PAGE_SHIFT, amdgpu_sg_segment_size(),
GFP_KERNEL);
+
if (r)
goto release_sg;
--
2.25.1
